In coniferous wood and fast growing hard wood which are soft and have a low density, their surface properties such as hardness and abrasion resistance may become a problem, especially when used for flooring boards, furuitures and interior finished materials. Soft wood with useful surface properties can be obtained by comperssing the wood in the direction perpendicular to the grain. When a compressed specimen is dried under restraint, the stress gradually decreses until it has disappered. The deformation is fixed in the deformed state (drying set). However, this drying set is only apparent, because it is almost recovered by boiling. Therefore, the permanent fixation of deformation is essential to use densified wood. One of the most effective ways of fixing deformation is high pressure steam treatment. In this study, an apparatus for the production of densified wood by high-pressure steam treatment utilizing moisture in wood was developed. Using a hot press equipped with an air-tight O-ring seal and a high frequency heating device, compression and hygro-thermal treatment can be done simultaneously. When a thin wood specimen with 17% moisture content was compressed, almost no recovery of deformation was observed after only 1 min of heating with the hot press at 200ﾟC or 8 min at 180ﾟC.However, the fixation was insufficient for dry specimens, so that moisture in the wood was considered to act so as to fix the deformation. On the other hand, to increase the temperature inside the specimen with 60mm thickness up to 200ﾟC it took about 80min by hot-pressing, but about 4min in combination with high frequency heating. Hardness showed an increse of about three times by compressing to about 50% of the initial thickness. The strength properties also increased remarkably. Only a slight yellowing and darkening occurred in the specimens steamed at 180ﾟC for 8 min.